What it means
The HV battery pack cooling fan 1 sense circuit reports a sense circuit intermittent/erratic fault. Fan speed feedback is unreliable.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The hybrid battery cooling fan circulates air through the high-voltage battery pack, and its sense circuit reports fan 1 speed to the control module. P0BCB sets when that feedback becomes intermittent or erratic, commonly because the connector is loose, the ground reference is noisy, or vibration interrupts terminal contact.
Common causes
Most likely first.
- Connector not seated
- Noisy ground reference
- Connector with intermittent contact under vibration
Symptoms
- EV/hybrid system warning light on
- Reduced power output or limp mode
- Charging may fail or be slowed
- Reduced electric range
How to diagnose it
- Save freeze-frame data and review fan 1 command and speed feedback, if available, for dropouts and note whether they coincide with vibration or particular operating conditions.
- With the vehicle powered down as specified by service information, inspect the fan 1 connector for incomplete seating, corrosion, or terminals that can move in the housing.
- Inspect the accessible sense wiring and ground reference for chafing, looseness, or damage that could make feedback unstable.
- Monitor fan 1 feedback while gently checking accessible low-voltage wiring and connector stability, without disturbing high-voltage components.
- If no external fault is found, test the sense and ground/reference circuits and fan tachometer using the manufacturer's procedure.
Common fixes
- Fully seat and secure the fan 1 connector.
- Clean or repair loose or corroded fan 1 terminals.
- Repair damaged sense wiring or a poor ground/reference connection.
- Replace the fan assembly if its tachometer remains intermittent with a sound circuit.
Can I keep driving?
Avoid heavy driving and charging if the warning returns or the vehicle limits power, since both can increase battery heat. Unstable fan feedback can trigger protective operation and leave cooling performance uncertain.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.